The subject matter herein relates generally to gas measuring devices and methods of operating gas measuring devices.
Gas measuring devices having sensors that detect certain chemicals or gases in air are utilized in many applications. For example, the detection of noxious gases such as carbon monoxide, hydrogen sulfide, nitrogen oxides, and the like is desirable so that a signal can be generated indicating the presence of such gases. Appropriate steps can then be taken to mitigate their effect or to remove persons from the presence of the gases.
One type of gas measuring device used to detect gas presence is a metal oxide semiconductor to provide early warning of the development of an explosion hazard (e.g. escaping flammable gas) or the presence of toxic gases or vapors in ambient air. The device typically includes a sensor provided on a heated substrate and that includes two metallic electrodes connected to the sensor. The presence of gas posing a hazard is detected by a sensible change in the resistance of the sensor by means of the electrodes that are incorporated in a suitable electric circuit.
The reactions that allow the detection of target gases normally involve the oxidation of the target gas at the semiconductor (oxide) surface and a change in the electrical properties of the material. However, conventional sensors may be impacted by changes in temperature or humidity. Maintaining a constant temperature of the sensing element has proven problematic. At least some known devices have overcome such problems by superheating the sensor and maintaining the sensor at a superheated temperature, such that the sensor is less effected by changes in temperature. However, maintaining the sensor at superheated temperatures requires more power to operate the device.
A need remains for a gas measuring device and sensor that may be manufactured and operated in a cost effective and reliable manner.